The present invention relates to a new principle for the detection, quantification, and monitoring of gas-borne materials capable of exothermic reactions. The methods, apparatus, and applications following from this principle and encompassed by this patent are intended for applications to gases, vapors, aerosols, and mixtures thereof.
Throughout numerous industries and in diverse workplaces, hazards arise from detonations and/or deflagrations involving gas-borne materials. The hazards occur when exothermic chemical reactions (i.e. combustion) of these materials are initiated under conditions which permit the reaction chemistry to become self-sustaining thereby allowing it to propagate through the gas. In the case of detonations, both heat and a large pressure rise accompany the propagation of a shock wave. For deflagrations, the propagation is associated principally with temperature rise and a pressure rise for rapidly moving deflagrations.
In practical settings, ignition sources for the exothermic chemistry can be due to electrostatic discharge (e.g., arcs, sparks from motors, static discharge due to accumulated charge), glowing or open flame (e.g. cigarette, welding torch), hot surfaces, or even spontaneous combustion. Examples of accidents include grain elevator damage or total destruction due to dust explosion, plastics manufacturing, shaping, or other processing facility explosions, coal mine explosion, petrochemical processing plant explosion or fire, gas storage or transfer location explosions, and innumerable less spectacular accidents in which the extent of deaths and injuries and damage to structures, materials, and equipment are more limited.
To avoid accidental detonation or deflagration, a number of different steps are available, depending upon the particular circumstance. Where feasible, measures are taken to prevent hazardous concentrations of combustible materials from accumulating in the local atmosphere. Whenever this is unreliable or impractical, as in the transport and handling of fine particulate materials, at chemical processing, transfer, and storage locations, in hazardous waste sites, and elsewhere, warning sensors and detonation/deflagration suppressers are commonly utilized. In all cases, extensive measures to avoid any ignition sources are generally taken. For some circumstances such as welding of tanks previously containing combustible liquids and industrial processes, hazardous conditions are always possible and there is little that can be done other than conduct the processes or activities in a prudent manner even if the hazard itself is poorly quantified.
Common to almost all detonation/deflagration hazard avoidance measures are the needs for sensors to indicate the status of the potential for hazard. When preventative measures are utilized, methods to determine the effectiveness of those measures are required. Regardless of whether sensing the potential for detonation and deflagration is the primary measure, the secondary measure, or utilized in ventilation or process control, the detectors must be effective, reliable, accurately indicate the actual hazard, and require a minimum of maintenance.